A rail vehicle transportation system may include tracks over which rail vehicles travel. These tracks may cross routes of other transportation systems, such as road or highway systems over which automobile and/or pedestrian traffic may pass. To prevent collisions between rail vehicles and automobiles, crossing gates may be provided at locations where the tracks intersect roads, with the crossing gates configured to impede automobiles from crossing the tracks while a rail vehicle is traveling on the tracks at or near the crossing.
Some known railroad crossings use a warning predictor track circuit that detects motion of a train towards the crossing. Warning predictors may calculate the time of train arrival at the crossing based on the detected motion, and activate the crossing warning devices (lights, gates, bells, or the like) a specified minimum amount of time prior to train arrival at the crossing. The minimum amount of time may be set by a government regulation, or set to exceed a government regulation. Crossing predictors are commonly used where there are mixed train types (freight, passenger, or the like) and/or where train speeds vary dramatically.
In some systems, for example rail systems that use catenaries or third rails to provide energy to rail vehicles, electrical interference may be too high for predictor systems to function accurately. Thus, in some applications, crossing gates or lights may be activated based on train occupancy within a given distance of a crossing, without respect to relative speed or arrival time of a train at a crossing. If track circuits that simply activate the crossing based on train occupancy are used (as opposed to detecting train motion), the warning times provided at the crossing can vary significantly depending upon train speed. Long warning times are undesirable because of the unnecessary delay caused to motorists, and also because overly long warning times may tempt impatient motorists to drive around crossing gates and/or disregard audible or visible warnings if the motorists do not see any trains approaching after some period of time.
Stations for train stops for picking up or dropping off passengers may be positioned near crossings, for example, to allow passengers to park close to the station. Areas of track monitored by track detection circuits for train movements and/or occupancy may be referred to as an approach and an island. The island may be tens or hundreds of feet on either side of a crossing (e.g., a crossing spanning the width of a road or highway). The approach, in turn, may be hundreds or thousands of feet on either side of the crossing (positioned outward of the island with respect to the highway). Problems, difficulties, or shortcomings associated with crossing operation may be exacerbated in situations where stations at which a vehicle (e.g., train) will stop are close to a crossing.
Crossing warnings may be activated various different ways in response to information from track detection circuits. For example, some track circuits may activate a crossing warning as soon as the approach is occupied. As another example, some track circuits may activate the crossing warning when motion is detected within the approach. As one more example, other track circuits may activate a crossing warning when a measured or determined motion indicates that a train will arrive at a given crossing in a prescribed amount of time (e.g., 20 seconds). Such systems have a number of shortcomings when a train stops at a station within the range of the detection circuits.
For example, if a crossing warning is activated due to train occupancy, the crossing warning will be activated the entire time the train is within the range of the detector circuit, even when the train is stopped at a station. As a result, traffic along a highway through the crossing may be stopped unnecessarily while the train dwells or remains at the station. Further, such a long warning time may tempt or encourage motorists to drive around the crossing gates, especially if the motorists see a stopped train. This results in a dangerous situation as, for example, trains may be approaching the crossing on adjacent tracks from the same or different direction.
As another example, if a crossing is equipped with a track detection circuit that activates the crossing due to train motion in the approach (and/or based on an estimated speed, distance, or arrival time at a crossing of a train detected within the approach), the warning device (e.g., a gate) may activate when the train enters the approach and subsequently deactivate when the train stops at the station. The repeated raising and lowering of a gate without a train passing through the crossing may confuse motorists and result in unsafe driving behavior. Further, the activation and deactivation may result in gate pump (e.g., raising the gate after a lowering has been initiated but before the lowering has completed), which may result in excessive wear on the crossing gate mechanism.
Further still, such track detection circuits or systems may be unable to detect the presence or movement of a train in time to activate a crossing warning after the train leaves the station. For example, if the station is close to the crossing, the train may arrive before the warning is fully activated or before a sufficient warning time has elapsed. Presently, when a train leaves a station within a detection range of a track detection system, the operator may move the train slowly toward the crossing until the detection of motion or detection of occupancy (e.g., occupancy within the island) may activate the crossing warning device, at which point the train may then proceed through the crossing. However, the island may have a range extending a short distance (e.g., tens of feet) from a highway or road. Thus, a train may be moving toward a highway or road a short distance from the highway or road with a crossing warning not activated. Motorists crossing the tracks and seeing a nearby train moving towards them may have a panic reaction and cause an accident.
Further still, federal (or other) regulations may require a minimum warning time before a train passes through a crossing. For example, the United States presently requires provision of a minimum of 20 seconds warning time (defined as the time from the start of a crossing warning to when the train occupies a highway). Presently, this warning time may be violated by operator error, for example, if an operator does not wait a sufficient amount of time before traversing a crossing.